Filter for collecting chlorinated organic compound

ABSTRACT

The collecting filter can capture and collect various chlorinated organic compounds in both particulate form and gaseous form contained in a fluid at the same time, and is easy to extract the collected chlorinated organic compounds therefrom. This collecting filter  7  is provided with a fluid-permeable molded body containing fibers and an inorganic binder for binding the fibers to one another, and a hydrophobic material having higher hydrophobicity than that of the fibers and the inorganic binder, which is retained in the molded body. Various chlorinated organic compounds such as dioxins in both particulate form and gaseous form contained in the sample gas are captured and collected upon passage through the collecting filter  7.

TECHNICAL FIELD

The present invention relates to a collecting filter, in particular, afilter for collecting a chlorinated organic compound.

BACKGROUND ART

An exhaust gas generated from incineration facilities for incineratingwastes such as industrial wastes and general home garbage containsvarious chlorinated organic compounds such as dioxins,polychlorobiphenyls, chlorophenol and chlorobenzene.

Herein, the word, dioxins, is a general term ofpolychlorodibenzo-para-dioxins (PCDDs), polychlorodibenzofurans (PCDFs)and the like, and is an environmental pollutant which is extremelytoxic, as well known. Inter alia, 2,3,7,8-tetrachlorodibenzo-para-dioxin(T₄CDD) is known as a most toxic substance. In addition,polychlorobiphenyls are similarly an environmental pollutant which isconsiderably toxic. Inter alia, coplanar polychlorobiphenyls (Co-PCBs)are recognized as a most toxic substance like dioxins. In the presentapplication, the word “dioxins” is used to include coplanarpolychlorobiphenyls (Co-PCBs) in addition topolychlorodibenzo-para-dioxins (PCDDs) and polychlorodibenzofurans(PCDFs) according to Article 2 of “Law Concerning Special Measuresagainst Dioxins” established in 1999 as Law No.105 in Japan.

On the other hand, although chlorinated organic compounds such aschlorophenol and chlorobenzene are less toxic as compared with dioxins,it has been found that they are easily converted into dioxins undercertain conditions, for example, using various elements contained in flyashes as catalyst in an incinerator in a temperature range of an exhaustgas. Therefore, they are recognized as environmental pollutants likedioxins. For this reason, from a viewpoint of environmental protection,it becomes an urgent issue to establish a countermeasure for removingthe aforementioned various chlorinated organic compounds from a fluidsuch as an exhaust gas and waste-water. At the same time, it is alsourgent in global scale to establish a procedure for analyzingchlorinated organic compounds contained in such a fluid.

Meanwhile, when chlorinated organic compounds contained in a fluid areanalyzed, first, it is necessary to obtain a sample precisely andexactly from a fluid to be analyzed. For example, when chlorinatedorganic compounds contained in an exhaust gas are analyzed, it isnecessary to collect a prescribed amount of a sample gas from a spacecontaining the exhaust gas, for example, a flue through which theexhaust gas is flown, and assuredly capture all various chlorinatedorganic compounds contained in this sample gas without leakage. Inparticular, the aforementioned dioxins, which are environmentalpollutants, are contained in the sample gas at an extremely smallamount, and dioxins are in various forms such as particulate form andgaseous form, and there are many kinds of dioxins. Therefore, withoutprecise collection of them, analysis results having high reliance cannotbe expected. Further, since there is a possibility that coplanarpolychlorobiphenyl is contained in the atmospheric air at a largeamount, when a sample gas is contaminated with the air containingcoplanar polychlorobiphenyl, analysis results having high reliancecannot be expected similarly. For this reason, in order to guarantee theaccuracy of the analysis results, Japan, US and each country of Europerespectively have been officially establishing a method, for example,for collecting a necessary sample for analyzing a chlorinated organiccompound such as dioxins contained in an exhaust gas.

For example, Japanese Industrial Standard JIS K 0311:1999 established onSep. 20, 1999 stipulates “Method for determination of tetra- throughocta-chlorodibenzo-p-dioxins, tetra- through octa-chlorodibenzofuransand coplanar polychlorobiphenyls in stationary source emissions”, andspecifically exemplifies a device for collecting a sample gas includinga chlorinated organic compound such as dioxins therein. This collectingdevice is provided mainly with a collecting tube for collecting a samplegas from a flue of an incineration equipment through which an exhaustgas is flown, a first captor provided with a filter material forcapturing a chlorinated organic compound mainly in a particulate formcontained in the sample gas collected by the collecting tube, and asecond captor for capturing a chlorinated organic compound in a gaseousform which is hardly captured by the first captor. Herein, the secondcaptor is provided mainly with a liquid capturing portion composed of aplurality of glass impingers containing an absorbent liquid and anadsorptive capturing portion arranged with an adsorbent (e.g.styrene-divinylbenzene copolymer sold under trade name of XAD-2), and isconstructed that a chlorinated organic compound in a gaseous form whichis not captured by the first captor can be captured by the absorbentliquid contained in the impingers and the adsorbent.

Since such a collecting device has a complicated construction providedwith the first captor and the second captor, and is expensive because ofuse of many glass instruments, the device is utilized repeatedly in manycases. In this case, since it is required to keep the respective memberssuch as impingers clean in order to retain the reliance of measurementdata, a preparatory work such as washing procedure before collection ofa sample gas becomes very troublesome. In addition, upon capturing of achlorinated organic compound in a gaseous form contained in a sample gasby the second captor, it is necessary to cool the second captor using acoolant such as dry ice, and the procedure of collecting a sample itselfbecomes very complicated. Further, after collection of a sample gas, itis necessary to extract a chlorinated organic compound captured by thefirst captor and the second captor. Herein, since it is necessary toextract individually the chlorinated organic compounds captured by thefirst captor and the second captor having a complicated construction,respectively, the extraction procedure itself is troublesome, and ittakes a long time until completion. In addition, the reliance ofanalysis results depends on skill of extraction procedure in many cases.Further, since this collecting device is composed of two types ofcaptors of the first captor and the second captor, the device isinevitably scaled up. Moreover, since the device uses many glassinstruments and therefore is easily damaged, handling at sample gascollection and conveyance are also difficult.

On the other hand, Environmental Protection Agency (EPA) of USA andEuropean Committee for Standardization (CEN) also stipulate their ownofficial methods. However, collecting devices shown therein aredifferent from the aforementioned Japanese device in details, but areslightly different in respect of complicated construction and difficulthandling.

The object of the present invention is to simultaneously capture andcollect various kinds of chlorinated organic compounds in bothparticulate form and gaseous form contained in a fluid, and easilyextract the collected chlorinated organic compounds.

DISCLOSURE OF THE INVENTION

A filter for collecting chlorinated organic compound of the presentinvention is for selecting and collecting a chlorinated organic compoundcontained in a fluid from the fluid. The filter comprises afluid-permeable molded body containing fibers and an inorganic binderfor binding the fibers to one another, and a hydrophobic material havinghigher hydrophobicity than that of the fibers and the inorganic binder,which is retained in the molded body.

Since the filter for collecting chlorinated organic compound of thepresent invention is such that a hydrophobic material is retained in afluid-permeable molded body, a fluid containing various chlorinatedorganic compounds such as dioxins in both particulate form and gaseousform can pass through the filter. Thereupon, the aforementioned variouschlorinated organic compounds in both forms contained in the fluid arecaptured simultaneously by the fibers and the inorganic binder containedin the molded body as well as the hydrophobic material retained in amolded body, and accordingly are selected from the fluid. That is,chlorinated organic compounds in both particulate form and gaseous formcontained in the fluid are collected by the collecting filter. Collectedchlorinated organic compounds can be extracted by applying variousextracting procedures to the collecting filter.

The fibers used in this collecting filter are, for example, at least onekind of fibers selected from the group consisting of glass fiber,alumina fiber and silica fiber. It is preferable that an average aspectratio of the fibers is usually 1,000 to 10,000.

The inorganic binder used in this collecting filter has an adsorbingcapability, for example, to a chlorinated organic compound. It ispreferable that the inorganic binder has an adsorbing capability, forexample, to a tar. The inorganic binder used herein is, for example, atleast one kind of compounds selected from the group consisting ofalumina, zeolite and silicon dioxide. In addition, the inorganic binderis usually particulate.

Further, it is preferable that the hydrophobic material used in thiscollecting filter has an adsorbing capability to a chlorinated organiccompound. The hydrophobic material is, for example, at least one kind ofmaterials selected from the group consisting of activated carbon,graphite and styrene-divinylbenzene copolymer.

The molded body constituting this collecting filter has usually a bulkdensity of 0.1 to 1 g/cm³. In this collecting filter, the hydrophobicmaterial is usually retained at 0.01 to 10.0% by weight of the moldedbody.

A preferable embodiment of this collecting filter is, for example, suchthat the fibers are activated alumina fibers, the inorganic binder isparticulate activated alumina, and the hydrophobic material is powderyactivated carbon. In this embodiment, a bulk density of the molded bodyis preferably, for example, 0.3 to 0.7 g/cm³.

The collecting filter of the present invention is formed into, forexample, a cylinder having one closed end.

A process of the present invention is a process for preparing a filterfor selecting and collecting a chlorinated organic compound contained ina fluid from the fluid. The process comprises a step of preparing amolding material containing fibers and an inorganic binder for bindingthe fibers to one another, a step of molding the molding material into apredetermined shape and sintering this to obtain a molded body, and astep of making the molded body retain a hydrophobic material havinghigher hydrophobicity than that of the fibers and the inorganic binder.

In such a process for producing the filter, since the aforementionedmolding material is molded and thereafter sintered, a molded body havingfluid permeability can be prepared. Since this molded body contains thefibers and the inorganic binder, and retains the hydrophobic materialhaving higher hydrophobicity than that of the fibers and the inorganicbinder, when a fluid containing various chlorinated organic compoundssuch as dioxins in both particulate form and gaseous form passestherethrough, the molded body can capture the chlorinated organiccompounds and select them from the fluid. In addition, the chlorinatedorganic compounds in both particulate form and gaseous form collected bythis molded body can be easily extracted by applying various extractingmethods to the molded body.

In one embodiment of this process, for example, at least one of theelements including the fibers and the inorganic binder is alumina, and atemperature at sintering is set at 150 to 170° C.

Also, this process further comprises a step of immersing the molded bodyin an aqueous dispersion of the inorganic binder and then drying themolded body, before the step of making the molded body retain thehydrophobic material.

A collector of the present invention is for collecting a chlorinatedorganic compound contained in a fluid which is flown in a transportationtube, and is provided with a filter having fluid permeability forpassing the fluid from the transportation tube therethrough, and acontainer which accommodates the filter and has an outlet fordischarging the fluid which has passed through the filter to theoutside. Herein, the filter is provided with a molded body containingfibers and an inorganic binder for binding the fibers to one another,and a hydrophobic material which is retained in the molded body and hashigher hydrophobicity than that of the fibers and the inorganic binder.

In the collector of the present invention, a fluid from thetransportation tube is passed through the filter in the container and,thereafter, discharged through the outlet to the outside. Thereupon,various chlorinated organic compounds such as dioxins in bothparticulate form and gaseous form contained in the fluid are capturedsimultaneously by the fibers and the inorganic binder constituting themolded body as well as the hydrophobic material retained in the moldedbody, selected from the fluid, and collected by the filter. The variouschlorinated organic compounds collected by the filter can be easilyextracted by applying various extracting procedures to the filter.

In this collector, the filter is, for example, a cylinder having anopening for inserting the transportation tube into one side and closedin the other side.

A method of the present invention is a method for collecting chlorinatedorganic compound contained in a fluid flowing in a transportation tube.The method comprises a step of passing the fluid from the transportationtube through a filter provided with a fluid-permeable molded bodycontaining fibers and an inorganic binder for binding the fibers to oneanother, and a hydrophobic material having higher hydrophobicity thanthat of the fibers and the inorganic binder, which is retained in themolded body.

Since such a method for collecting chlorinated organic compound uses thefilter provided with the aforementioned molded body containing thefibers and the inorganic binder and the hydrophobic material retained inthis molded body, when the fluid from the transportation tube passesthrough the filter, various chlorinated organic compounds such asdioxins in both particulate form and gaseous form contained therein arecaptured and collected by the filter at the same time. The variouschlorinated organic compounds collected by the filter can be easilyextracted by applying various extracting procedures to the filter.

Other objects and effects of the present invention will be described inthe following detailed explanation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a brief construction view of an apparatus for collectingchlorinated organic compound in which the collector in accordance withone embodiment of the present invention is adopted.

FIG. 2 is a front view of the collector.

FIG. 3 is a longitudinal cross-sectional view of the collector.

FIG. 4 is a IV-IV cross-sectional view of FIG. 2.

FIG. 5 is an electron microscopic photograph of a part of the moldedbody obtained in Example.

FIG. 6 is an electron microscopic photograph of a part of the collectingfilter obtained in Example.

FIG. 7 is a graph showing results of investigation of relationshipbetween an amount of water in a sample gas and a capturing rate inExample.

FIG. 8 is a graph showing results of investigation of relationshipbetween an average carbon monoxide concentration in a sample gas and acapturing rate in Example.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a brief construction of an apparatus for collectingchlorinated organic compound in which one embodiment of collector ofchlorinated organic compound according to the present invention isadopted. This collecting apparatus 1 is for collecting a chlorinatedorganic compound contained in a sample fluid (sample gas) such as anexhaust gas, among a fluid. In the figure, the collecting apparatus 1 isprovided mainly with a collecting tube 2, a collector 3 (one embodimentof collector according to the present invention) and an aspirator 4.

The collecting tube 2 is made of, for example, a borosilicate glass or atransparent quartz glass, and has a cooling device 5 for cooling thesample gas which passes through the interior thereof.

Referring to FIG. 2, FIG. 3 and FIG. 4, details of the collector 3 willbe explained. In the figures, the collector 3 is provided mainly of aholder (one example of container) 6, a collecting filter 7 (oneembodiment of filter for collecting chlorinated organic compoundaccording to the present invention) for capturing and collecting achlorinated organic compound contained in a sample gas, which isarranged in the holder 6, an introducing tube 8 (one example oftransportation tube) for introducing the sample gas transported via thecollecting tube 2 into the collecting filter 7 and a fitter 9 forfitting the introducing tube 8 to the holder 6.

The holder 6 is a generally cylindrical container made of a transparentglass, and has mainly a body 10 which can accommodate a collectingfilter 7, a fitting portion 11 into which the fitter 9 is fitted, and adischarging portion 12 for discharging the sample gas.

The fitting portion 11 is disposed integrally at an end portion of thebody 10, and its diameter is smaller as compared with the body 10. Thisfitting portion 11 has a thread groove 11 a on its outer circumferentialsurface, and has an opening 11 b at its end.

The discharging portion 12 is disposed integrally at other end of thebody 10, and has a discharging path (one example of outlet) 12 a fordischarging the sample gas to the outside, and a branch path 12 b. Thebranch path 12 b is for inserting a temperature-measuring instrument 27(FIG. 1) such as a thermometer and a thermocouple for measuring atemperature of the sample gas flowing in the discharging portion 12,into the discharging portion 12.

The collecting filter 7 is a cylindrical porous molded body having oneclosed end and an opening 7 a for introducing a sample gas at other end,that is, a porous cylindrical filter. The closed end side of thecollecting filter 7 is inserted in the body 10 of the holder 6 throughthe opening 11 b while the opening 7 a side is supported by the fitter9. A size of the collecting filter 7 is not particularly limited, butusually a length is set to be 50 to 150 mm, an outer diameter of the endon the opening 7 a side is set to be 12 to 35 mm, an outer diameter ofthe closed end side is set to be 10 to 30 mm, and a thickness is set tobe 1 to 10 mm. The collecting filter 7 is formed into a taper shape suchthat an outer diameter of the closed end side is set to be smaller thanan outer diameter of the end on the opening 7 a. Details of thecollecting filter 7 will be described later.

The introducing tube 8 is a tubular member made of a glass like theholder 6, and is detachable from the opening 7 a of the collectingfilter 7. That is, this introducing tube 8 has a connecting portion 13for connecting to an end of the collecting tube 2 at its one end, andits other end is detachably inserted into the opening 7 a of thecollecting filter 7 through the fitter 9.

The fitter 9 has a first support 14 for supporting the collecting filter7 in the holder 6, and a second support 15 for fitting the introducingtube 8 into the first support 14. The first support 14 is a member madeof a resin or a metal, and has a hole portion 14 a for supporting theopening 7 a side end of the collecting filter 7. A thread groove 14 b isformed on an inner circumferential surface of the hole portion 14 a. Thefirst support 14 is screwed to the thread groove 11 a on a fittingportion 11 side of the holder 6 by the thread groove 14 b thereof. Inaddition, the first support 14 has a projecting portion 16 which isprojected toward a left direction in FIG. 3. The projecting portion 16has a through hole 16 a through which a tip portion of the introducingtube 8 can be inserted, and a thread groove 16 b is formed on the outercircumferential surface thereof.

On the other hand, the second support 15 is a member made of a resin ora metal like the first support 14, and is formed into a lid-like shapein which a thread groove 15 a is formed on the inner circumferentialsurface thereof. The second support 15 has a through hole 15 b throughwhich the introducing tube 8 is inserted. This second support 15 withthe introducing tube 8 inserted into the through hole 15 b, is screwedto the thread groove 16 b of the projecting portion 16 of the firstsupport 14 by the thread groove 15 a.

The collecting filter 7 fitted into the above-described collector 3 canbe removed from the holder 6. In this case, the second support 15 of thefitter 9 is removed from the first support 14, and the introducing tube8 is pulled out of the collecting filter 7. Then, by removing the firstsupport 14 from the holder 6, the collecting filter 7 is removed fromthe holder 6 while being supported by the first support 14.

The aspirator 4 is provided with an exhaust path 20 and a suction device21. The exhaust path 20 has one end connected to the discharging path 12a of the collector 3 using a tubular joint 22, and has a condenser 23and a trap 24 in this order from the collector 3 side. The suctiondevice 21 is attached to other end of the exhaust path 20, and has asuction pump 21 a and a gas meter 21 b in this order. The suction pump21 a has a flow rate regulating function, and can be continuously usedfor 24 hours or longer. The gas meter 21 b is for measuring a flow rateof a sample gas, and can measure a range of 10 to 40 l/min with accuracyof 0.1 l/min level.

Next, the collecting filter 7 used in the aforementioned collector 3will be explained in detail. The collecting filter 7 is provided with amolded body of a three-dimensional network structure having afluid-permeability (a gas-permeability in this embodiment), and ahydrophobic material retained in the molded body.

The molded body constituting the collecting filter 7 contains fibers (agroup of fibers) and an inorganic binder. The fibers used herein do notsubstantially chemically react with various chlorinated organiccompounds such as dioxins and a precursor thereof. Examples of thefibers include glass fiber, alumina fiber (particularly activatedalumina fiber) and silica fiber. These fibers may be used solely or incombination of two or more types of them. A fiber diameter and aspecific surface area of the fibers are not particularly limited.

An average aspect ratio (length/diameter) of this fibers is preferably10,000 or smaller, particularly preferably 1,000 to 10,000. When theaverage aspect ratio of the fibers exceeds 10,000, a pressure loss isincreased during collection of a sample fluid (sample gas), and there isa possibility that isokinetic suction prescribed in the aforementionedJIS Standard (JIS K 0311:1999) cannot be preformed.

On the other hand, the inorganic binder contained in this molded bodyhas a nature of binding fibers to one another to incorporate a group offibers and thereby impart a certain molded shape to the group of fibers.That is, the inorganic binder functions as a binder for retaining thegroup of fibers in a certain molded shape. In this embodiment, morespecifically, the inorganic binder make the group of fibers set into theaforementioned shape of the collecting filter 7, that is, a cylindricalshape having one closed end.

An inorganic binder usable herein is not particularly limited as far asit has the aforementioned performance, and does not substantiallychemically react with a chlorinated organic compound like the fibers,but an inorganic binder having an adsorbing capability, in particular,an adsorbing capability for a chlorinated organic compounds ispreferable. Examples of the inorganic binder having such a adsorbingcapability include alumina (in particular activated alumina), zeolite,silicon dioxide (silica), acid clay and apatite. These inorganic bindersmay be used solely or in combination of two or more of them. Inaddition, a form of the inorganic binder is not particularly limited,but usually a particulate inorganic binder is used.

Herein, zeolite is hydrous aluminosilicate represented by the generalformula X_(m)Y_(n)O_(2n)·sH₂O. In the general formula, X represents Na,Ca or K, Y represents Si+Al, and s is not constant. As such zeolite,synthetic zeolite is preferably used.

Among the aforementioned inorganic binders, in the present invention, aninorganic binder having tar-adsorbing capability is particularlypreferably used. When an inorganic binder having such a characteristicis used, the collecting filter 7 can effectively adsorb a tar producedand derived from, for example, carbon monoxide contained in a sample gas(details of the tar will be described later), and can more assuredlycapture and collect various chlorinated organic compounds such asdioxins dissolved in the tar. Examples of the inorganic binder which canadsorb a tar include alumina, zeolite and silicon dioxide. As thealumina, activated alumina is particularly preferably used. Theseinorganic binders which can adsorb a tar may be used solely or incombination of two or more of them.

A bulk density of the aforementioned molded body containing the fibersand the inorganic binder is preferably set at 0.1 to 1 g/cm³, morepreferably 0.3 to 0.7 g/cm³. In the case where the bulk density of themolded body is smaller than 0.1 g/cm³, a part of chlorinated organiccompounds contained in a sample gas is passed through the collectingfilter 7 in some cases, and it becomes difficult to collect chlorinatedorganic compounds contained in the sample gas without substantialleakage, in some cases. Conversely, in the case where the bulk densityexceeds 1 g/cm³, in the collecting filter 7, when a particulatesubstance contained in a sample gas is captured, a pressure loss may beincreased, and there is a possibility that the sample gas hardly passestherethrough. As a result, there is a possibility that it becomesdifficult to perform isokinetic suction prescribed in the aforementionedJIS Standard (JIS K 0311:1999), in the collecting filter 7. In addition,in an extraction procedure described later for extracting thechlorinated organic compounds collected by the collecting filter 7, anextraction rate may be reduced.

On the other hand, the hydrophobic material retained in theaforementioned molded body does not substantially chemically react witha chlorinated organic compound. The hydrophobic material is notparticularly limited as far as it has higher hydrophobicity than that ofthe aforementioned fibers and inorganic binder, but a hydrophobicmaterial having an adsorbing capability, in particular, adsorbingcapability for a chlorinated organic compound is preferable. As thehydrophobic material having such an adsorbing capability, at least onekind selected from the group consisting of, for example, activatedcarbon, graphite and styrene-divinylbenzene copolymer (e.g. trade name“XAD-2” of Sigma-Aldrich Corporation in U.S.A.) is preferable.Alternatively, as the hydrophobic material, a material having analkylsilyl group, for example, a material having an alkylsilyl grouphaving 8 to 18 carbon atoms may be used. Further, a form of thehydrophobic material is not particularly limited, but usually a powderyor particulate hydrophobic material is used.

It is preferable that the hydrophobic material is retained at usually0.01 to 10.0% by weight, preferably 0.05 to 5.0% by weight of the moldedbody. In the case where an amount of the hydrophobic material is smallerthan 0.01% by weight, there is a possibility that it becomes difficultto collect chlorinated organic compounds contained in a sample gas usingthe collecting filter 7 without substantial leakage if the sample gascontains a large amount of water. Conversely, in the case where anamount of the hydrophobic material exceeds 10.0% by weight, in thecollecting filter 7, there is a possibility that a pressure loss isincreased when a particulate substance contained in a sample gas iscaptured, and the sample gas hardly passes therethrough. As a result,there is a possibility that it becomes difficult to perform isokineticsuction prescribed in the aforementioned JIS Standard (JIS K 0311:1999),in the collecting filter 7. In addition, in an extraction proceduredescribed later for extracting chlorinated organic compounds collectedby the collecting filter 7, the extraction may become difficult, leadingto reduction in an extraction rate.

A preferable collecting filter 7 is such that powdery activated carbonas the hydrophobic material is retained in the molded body usingactivated alumina fibers as the fibers and particulate activated aluminaas the inorganic binder. In particular, the molded body having a bulkdensity in a range of 0.3 to 0.7 g/cm³ is most preferable.

The aforementioned collecting filter 7 can be usually prepared bypreparing the aforementioned molded body, and making this molded bodyretain the hydrophobic material. Specifically, the filter can beprepared as follows:

First, a molding material containing the aforementioned fibers andinorganic binder is prepared. Herein, a dispersion in which an inorganicbinder is dispersed in water is prepared, then fibers are added to thisdispersion to uniformly mix the inorganic binder and the fibers.Thereupon, it is preferable that a ratio of mixing the fibers and theinorganic binder is such that a bulk density of the desired molded bodyis appropriately adjusted to be in the aforementioned range.

Then, the resulting molding material is molded in a predetermined shape,that is, a cylinder having one closed end, to obtain a molded body. As amolding method herein, well known various molding methods such as a wetdie molding method can be adopted. Next, the resulting molded body isthermally treated to sinter to obtain the desired molded body. Atemperature at the time of sintering is not particularly limited, butwhen alumina is used for either one or both of the fibers and theinorganic binder, the temperature is preferably set in a range in whichthe alumina can be activated and converted into activated alumina,specifically, at 150 to 700° C.

The thus prepared molded body may further be immersed into an aqueousdispersion in which an inorganic binder is dispersed in water, and thensubjected to drying treatment. When the molded body is subjected to suchtreatment, the molded body is impregnated with an inorganic binder, anda molded body containing a larger amount of the inorganic binder can beprepared. In addition, by way of such treatment, the bulk density of themolded body can be adjusted in the aforementioned preferable range.Since such a molded body consequently contains a large amount of theinorganic binder, when an inorganic binder having the aforementioned taradsorbing capability is used, chlorinated organic compounds contained ina sample gas can be effectively captured without leakage even whenhydrocarbons or carbon monoxide as an unburnt substance described lateris contained at a large amount in the sample gas. A method of drying themolded body is not particularly limited, but usually it is preferable toadopt a method of heat-treating the molded body at around 150 to 700° C.to remove water.

Next, the resulting molded body is made to retain a hydrophobicmaterial. A method for doing so is not particularly limited, but forexample, there is a method of making the molded body retain ahydrophobic material using the aforementioned holder 6. In this method,the molded body obtained in the aforementioned step is charged into theholder 6 and the branch path 12 b is closed, and then a suction devicesuch as a suction pump is connected to the discharging path 12 a side.Subsequently, the suction device is operated to suck the interior of theholder 6 and, at the same time, a hydrophobic material is supplied intoan introducing tube 8. Thereby, the hydrophobic material supplied intothe introducing tube 8 is sucked in a direction toward the molded body,and is retained mainly in a direction of the inner circumferential sideto the thickness direction of the molded body. Thereupon, it ispreferable that an amount of the hydrophobic material to be suppliedfrom the introducing tube 8 is set so that a ratio relative to themolded body is in the aforementioned range.

Then, a method of using the aforementioned collecting apparatus 1, thatis, a method of collecting a chlorinated organic compound using theaforementioned collecting apparatus 1 will be explained. Herein, thecase where a sample gas is collected from an exhaust gas flowing in aspace, for example in a flue, of an incineration facility forincinerating wastes and various chlorinated organic compounds such asdioxins contained in the sample gas are collected, will be explained. Inthis case, as shown in FIG. 1, the tip portion of the collecting tube 2of the collecting apparatus 1 is inserted into a flue 25 through asample collecting port 25 a disposed in the flue 25. Thereupon, apacking 26 is attached to the collecting tube 2 to air-tightly seal thegap between the collecting tube 2 and the sample collecting port 25 a.In addition, a temperature-measuring instrument 27 such as a thermometerand a thermocouple is fitted into the branch path 12 b of the collector3.

In this state, the suction pump 21 a is operated to carry out isokineticsuction of a part of exhaust gas flowing in the flue 25 as a sample gasinto the collecting tube 2. Thereupon, it is preferable that atemperature, a flow rate, a pressure and an amount of water of theexhaust gas flowing in the flue 25 are measured to calculate anisokinetic suction amount according to, for example, JIS Z 8808 and,based on the calculation result, a suction flow rate by the suction pump21 a is adjusted. It is preferable that the flow rate set herein isappropriately regulated so that the result is appropriately monitoredwith the gas meter 21 b, and the isokinetic suction state is continued.

A sample gas which has flown into the collecting tube 2 is cooled by thecooling device 5, and is usually cooled to a temperature of a dioxinsproduction temperature or lower, for example, a temperature of 120° C.or lower. Thereby, in the collecting tube 2, new generation of dioxinsis prevented.

The cooled sample gas is flown into the collecting filter 7 from thecollecting tube 2 via the introducing tube 8 of the collector 3. Thesample gas which has been flown into the collecting filter 7 passesthrough the collecting filter 7, and then is flown into the body 10 ofthe holder 6 and, further, is flown toward the aspirator 4 via thedischarging path 12 a as indicated by arrows in FIG. 3. Thereupon,various dusts, as well as various chlorinated organic compounds such asdioxins in both particulate form and gaseous form contained in thesample gas are captured at the same time by the aforementioned fibersand inorganic binder contained in the molded body constituting thecollecting filter 7 and by the hydrophobic material, and are collectedfrom the sample gas.

Meanwhile, when a carbon compound such as unburnt hydrocarbons andcarbon monoxide (CO) is contained at a large amount in a sample gas, atar derived from the carbon compound is easily produced in the samplegas. In many cases, the tar dissolves various chlorinated organiccompounds including dioxins therein and takes them inside. For thisreason, when a collecting filter 7 not using an inorganic binder havingtar adsorbing capability, for example, a collecting filter composed of amolded body obtained by molding the aforementioned fibers using anorganic binder such as a cellulose binder is used, the filter can noteffectively capture a tar produced in the sample gas, and consequentlythere is a possibility that a part of tar contained in the sample gaspasses through the filter and is discharged to the outside. That is,there is a possibility that the part of tar and chlorinated organiccompounds dissolved therein are discharged to the outside without beingcollected by the filter. This is a phenomenon that the present inventorsfound out during a process to the present invention. It has been alsofound that, when an amount of an unburnt carbon compound is determinedusing carbon monoxide as an index, in particular, if the concentrationof carbon monoxide contained in a sample gas exceeds 150 ppm, such apassage of tar can occur remarkably.

To the contrary, the collecting filter 7 in accordance with thisembodiment, when the filter is composed of a molded body containing theaforementioned fibers and inorganic binder having tar adsorbingcapability, can capture also a tar contained in a sample gassubstantially without leakage, even if the concentration of an unburntcarbon compound in the sample gas is high (for example, even if theconcentration of carbon monoxide in the sample gas exceeds 150 ppm).That is, whether the concentration of an unburnt carbon compound in asample gas is high or low, this collecting filter 7 can capture andcollect various chlorinated organic compounds such as dioxins in bothparticulate form and gaseous form contained in the sample gassubstantially without leakage.

In addition, when rapidly cooled by spraying water in the flue 25, asample gas has an increased amount of water in some cases. However, evenin such a case, since the collecting filter 7 contains theaforementioned hydrophobic material, it can capture and collect variouschlorinated organic compounds such as dioxins in both particulate formand gaseous form contained in the sample gas substantially withoutleakage.

As described above, the sample gas from which dusts as well as variouschlorinated organic compounds in particulate form and gaseous form havebeen selected by the collecting filter 7 substantially without leakage,is subsequently flown from the discharging path 12 a toward theaspirator 4. Thereupon, a temperature of the sample gas flowing in thedischarging path 12 a is measured and managed by thetemperature-measuring instrument 27 fitted in the branch path 12 b.

The sample gas discharged from the discharging path 12 a is flown intothe exhaust path 20, and is further cooled with the condenser 23.Thereby, the moisture contained in the sample gas is condensed, and isstored in the trap 24. The sample gas from which the moisture has beenremoved like this is discharged to the outside from the gas mater 21 bvia the suction pump 21 a. Collection of a sample gas, that is, anexhaust gas with such a collecting apparatus 1 is usually preformed fora time corresponding to an amount of the exhaust gas presumed from adetection limit value of the chlorinated organic compounds (usually, anexhaust gas of 1 to 3 Nm³/3 to 4 hours).

When the concentration of a chlorinated organic compound contained inthe thus collected sample gas (exhaust gas) is analyzed, the collectingapparatus 1 is removed from the flue 25, and the collector 3 isseparated from the collecting apparatus 1. Further, the collectingfilter 7 is removed from the separated collector 3.

Then, the interiors of the collecting tube 2, the introducing tube 8 andthe holder 6 are washed using a solvent, and a washing solutionthereupon is maintained. In addition, chlorinated organic compoundscaptured by the collecting filter 7 of the collector 3 are extractedwith a solvent. Herein, a procedure for extracting chlorinated organiccompounds captured by the collecting filter 7 can be performed using,for example, a conventional Soxhlet's extractor. Alternatively, whenthis collecting filter 7 is set to be a miniature size as describedabove, since it can be accommodated in a high speed extractor cell, theextraction procedure can be rapidly performed using the high speedextractor.

When a bulk density of a molded body constituting the collecting filter7 is set in the aforementioned range and, a content of the hydrophobicmaterial is set in the aforementioned range, it is not necessary to setspecial extraction condition for shortening an extraction time, andcaptured chlorinated organic compounds can be rapidly dissolved in asolvent in a short time.

Upon analysis of chlorinated organic compounds, the aforementionedwashing solution and the extract obtained by the aforementionedextraction procedure are combined, and this is subjected to an analysisprocedure. As an analysis method in this case, a method using a gaschromatographic mass spectroscopy (GC/MS method) can be adoptedaccording to a method described in “Standard Measurement and AnalysisManual For Dioxins In Waste Treatment” (published in March, 1997 byJapan Waste Research Foundation) edited by Japanese Ministry of Healthand Welfare, Environmental Health Bureau, Water Supply and EnvironmentalSanitation Department, Environmental Maintenance Section, or a methodprescribed in Japanese Industrial Standard JIS K 0311:1999 (establishedon Sep. 20, 1999).

When another sample gas is collected using the collecting apparatus 1,for example, the collector 3 is replaced with a new one. In this case,since the collecting apparatus 1 can be used for collecting a nextsample gas by sufficiently washing only the collecting tube 2, thepreparatory work before sample gas collection is considerably alleviatedas compared with that carried out using conventional impingers. As aresult, a necessary time for collecting a sample gas can be considerablyshortened, and also a necessary cost for collecting a sample gas can beconsiderably reduced, as compared with those using conventionalimpingers. In addition, since this collecting apparatus 1, inparticular, the collector 3 has a simple construction as compared with aconventional complicated collecting apparatus, so that it is easy tohandle and transport. For this reason, when this collecting apparatus 1is used, a work of collecting a sample gas can be easily performed evenon a flue in which a conventional large scale collecting apparatus usingimpingers is difficult to be disposed.

The once used collector 3 can be reused repeatedly when the holder 6 andthe introducing tube 8 are sufficiently washed, and the collectingfilter 7 is replaced with a new one.

The aforementioned embodiment can be modified, for example, as follows:

-   (1) Although a cylindrical filter is used as the collecting filter 7    in the aforementioned embodiment, the present invention is not    limited to this. For example, the present invention can be carried    out in the same manner in the case the collecting filter 7 is formed    into a column-like or a disk-like shape.-   (2) Although the case where a chlorinated organic compound such as    dioxins contained in an exhaust gas (a sample gas) discharged from    an incinerator for wastes is collected was explained in the    aforementioned embodiment, the collecting filter, the collector and    the collecting method of the present invention can be similarly    utilized also in the case where a chlorinated organic compound in a    fluid other than an exhaust gas is collected. For example, the    collecting filter and the like of the present invention can be    similarly utilized also when a chlorinated organic compound    contained in an environmental air, as well as a chlorinated organic    compound contained in water such as factory waste-water, sea water,    fresh water and tap water and the like are collected.

When a chlorinated organic compound contained in water such as factorywaste-water is collected, a sample to be collected is a liquid sample.In this case, there is a possibility that the liquid sample containsvarious chlorinated organic compounds in various states such as aparticulate state, a foam state (that is, air-liquid mixed state) and adissolved state (that is, dissolved in water state), but the collectingfilter of the present invention can capture and collect variouschlorinated organic compounds in such various states at the same timefrom the liquid sample.

EXAMPLE

An alumina dispersion in water containing about 20% by weight ofparticulate alumina (inorganic binder) was prepared, and alumina fibers(containing 72% by weight of γ-alumina and 28% by weight of silica)having an average fiber diameter of 6 μm and an average aspect ratio of2,000 as fibers were added to this alumina dispersion in water to mixthem. The resulting molding material was molded into a cylinder havingone closed end, and sintered at 200° C. Thereby, a cylindrical moldedbody having air permeability of a weight of 8.5 g and a bulk density of0.38 g/cm³ was obtained in which the outer diameter of the opening endside was set to be 19 mm, the outer diameter of the closed end side wasset to be 18 mm, the thickness was set to be 5 mm and the length was setto be 120 mm, respectively. The alumina fibers and the particulatealumina contained in this molded body were 5.7 g and 2.8 g,respectively.

An electron microscopic photograph of a part of the resulting moldedbody is shown in FIG. 5. From FIG. 5, it is seen that this molded bodyhas a fine network structure (three-dimensional network structure)having air permeability, which was formed by binding of alumina fiberswith particulate alumina as an inorganic binder.

Next, the resulting molded body was further immersed in a dispersion inwater in which particulate alumina was dispersed at 20% by weight, andthen taken out and dried by heat-treating at 200° C. Thereby, a moldedbody having a weight of 12.8 g and a bulk density 0.6 g/cm³ wasobtained.

The resulting molded body was used in place of the collecting filter 7to prepare the collector 3 relating to the aforementioned embodiment,and the branch path 12 b of the collector 3 was closed to connect thesuction pump to the discharging path 12 a side. The suction pump wasoperated to suck the interior of the holder 6 and, at the same time,powdery activated carbon (trade name “Kuraray Coal PK-DN” manufacturedby Kuraray Chemical Co., Ltd.) was introduced into the introducing tube8. Thereby, 12 mg of powdery activated carbon was retained mainly fromthe inner circumferential side to the thickness direction of the moldedbody, to obtain the collecting filter 7.

An electron microscopic photograph of a part of the resulting collectingfilter 7 is shown in FIG. 6. From FIG. 6, it is seen that thiscollecting filter 7 has a structure in which powdery activated carbon isretained mainly on the inner circumferential side of the aforementionedmolded body.

Using the resulting collecting filter 7, the collector 3 for achlorinated organic compound relating to the aforementioned embodimentwas made, and this collector 3 was used to construct the collectingapparatus 1 relating to the aforementioned embodiment. This collectingapparatus 1 was used to collect several kinds of sample gases (exhaustgases) having different amounts of water and average carbon monoxideconcentrations from a flue of an incinerator duringincineration-treatment of wastes, and various chlorinated organiccompounds such as dioxins contained in each of the sample gases werecollected. Thereupon, a sample gas collecting apparatus provided with animpinger exemplified in JIS K 0311:1999 (hereinafter, referred to as“JIS-exemplified apparatus”) was connected to the later stage of thecollecting apparatus 1, so that the sample gas which had passed throughthe collecting apparatus 1 was discharged after passed through theJIS-exemplified apparatus. The aforementioned amount of water is a ratio(volume percentage (%)) of water steam contained in an exhaust gas, andis prescribed in JIS Z 8808:1995 (established on Mar. 1, 1995) “Methodof Measuring Dust Concentration in Flue Gas”. Conditions of collectingthe sample gases were according to conditions prescribed in JIS K0311:1999.

Chlorinated organic compounds collected by the collecting apparatus 1and the JIS-exemplified apparatus, respectively, were extracted by themethod according to JIS K 0311:1999, and quantitatively analyzedaccording to the analysis method prescribed in the same JIS. Then, anamount of chlorinated organic compounds (A) collected by the collectingapparatus 1 and an amount of chlorinated organic compounds (B) collectedby the JIS-exemplified apparatus were obtained, respectively, and acapturing rate (%) of chlorinated organic compounds collected by thecollecting apparatus 1 was obtained according to the following equation.The results are shown in FIG. 7 and FIG. 8. FIG. 7 shows therelationship between an amount of water of the sample gas and acapturing rate, and FIG. 8 shows the relationship between an averagecarbon monoxide concentration of the sample gas and a capturing rate.Capturing rate (%)=A/(A+B)×100

From FIG. 7 and FIG. 8, it is seen that since the collecting apparatus 1is provided with the aforementioned collecting filter 7, it can collectvarious chlorinated organic compounds including dioxins in bothparticulate form and gaseous form contained in the sample gasessubstantially without leakage, whether an average carbon monoxideconcentration in a sample gas is high or low (that is, although aconcentration of an unburnt carbon compound in a sample gas is high) andwhether an amount of water in a sample gas is large or small.

INDUSTRIAL APPLICABILITY

Since a filter for collecting chlorinated organic compound of thepresent invention is provided with a molded body containing fibers andan inorganic binder, and a hydrophobic material having higherhydrophobicity than that of the fibers and the inorganic binder, whichis retained in the molded body, it can capture and collect variouschlorinated organic compounds including dioxins in both particulate formand gaseous form contained in a fluid at the same time. In addition, thecollected chlorinated organic compounds can be easily extracted from thefilter.

The present invention can be practiced in other various forms withoutdeparting from a spirit and main features thereof. Therefore, theaforementioned embodiments or example are merely an example in allrespects, and are not to be interpreted as limitation. A scope of thepresent invention is indicated by claims, and is not restricted by thetext of the specification at all. Further, variations and modificationsbelonging to an equivalent scope of claims are all within the scope ofthe present invention.

1. A filter for selecting and collecting a chlorinated organic compoundcontained in a fluid from the fluid, comprising: a fluid-permeablecylindrical molded body having one closed end and containing fibers andan inorganic binder for binding the fibers to one another, and ahydrophobic material having higher hydrophobicity than that of thefibers and the inorganic binder, which is retained in the molded body,wherein the hydrophobic material is retained mainly in a direction ofthe inner circumferential side to the thickness direction of the moldedbody.
 2. The filter according to claim 1, wherein the fibers are atleast one kind of fibers selected from a group consisting of glassfiber, alumina fiber and silica fiber.
 3. The filter according to claim1, wherein the fibers have an average aspect ratio of 1,000 to 10,000.4. The filter according to claim 1, wherein the inorganic binder hasadsorbing capability for the chlorinated organic compound.
 5. The filteraccording to claim 1, wherein the inorganic binder has adsorbingcapability for a tar.
 6. The filter according to claim 1, wherein theinorganic binder is at least one selected from a group consisting ofalumina, zeolite and silicon dioxide.
 7. The filter according to claim1, wherein the inorganic binder is particulate.
 8. The filter accordingto claim 1, wherein the hydrophobic material has adsorbing capabilityfor the chlorinated organic compound.
 9. The filter according to claim8, wherein the hydrophobic material is at least one kind selected fromthe group consisting of active carbon, graphite andstyrene-divinylbenzene copolymer.
 10. The filter according to claim 1,wherein a bulk density of the molded body is 0.1 to 1 g/cm³.
 11. Thefilter according to claim 1, wherein the hydrophobic material isretained at 0.01 to 10.0% by weight of the molded body.
 12. The filteraccording to claim 1, wherein the fibers are activated alumina fibers,the inorganic binder is particulate activated alumina and thehydrophobic material is powdery activated carbon.
 13. The filteraccording to claim 12, wherein a bulk density of the molded body is 0.3to 0.7 g/cm³.
 14. A process for producing a filter for selecting andcollecting a chlorinated organic compound contained in a fluid, from thefluid, comprising steps of: preparing a molding material containingfibers and an inorganic binder for binding the fibers to one another,molding the molding material into a cylinder having one closed end andsintering this to obtain a molded body, and making the molded bodyretain a hydrophobic material having higher hydrophobicity than that ofthe fibers and the inorganic binder so that the hydrophobic material isretained mainly in a direction of the inner circumferential side to thethickness direction of the molded body.
 15. The process for producing afilter according to claim 14, wherein at least one of the elementsincluding the fibers and the inorganic binder is alumina, and atemperature at sintering is set at 150 to 170° C.
 16. The process forproducing a filter according to claim 14, which further comprises a stepof immersing the molded body with an aqueous dispersion of the inorganicbinder and then drying the body, before the step of making the moldedbody retain the hydrophobic material.
 17. A collector for collecting achlorinated organic compound contained in a fluid flowing in atransportation tube, comprising: a fluid-permeable filter for passingthe fluid from the transportation tube, and a container foraccommodating the filter, and having an outlet for discharging to theoutside the fluid which has passed through the filter, wherein thefilter is provided with a cylindrical molded body having an opening forinserting the transportation tube into one side and closed in the otherside and containing fibers and an inorganic binder for binding thefibers to one another, and a hydrophobic material having higherhydrophobicity than that of the fibers and the inorganic binder, whichis retained mainly in a direction of the inner circumferential side tothe thickness of the molded body.
 18. A method for collecting achlorinated organic compound contained in a fluid flowing in atransportation tube, comprising a step of: passing the fluid from thetransportation tube through a filter provided with a fluid-permeablecylindrical molded body having an opening for inserting thetransportation tube into one side and closed in the other side andcontaining fibers and an inorganic binder for binding the fibers to oneanother, and a hydrophobic material having higher hydrophobicity thanthat of the fibers and the inorganic binder, which is retained mainly ina direction of the inner circumferential side to the thickness directionof the molded body.